The facility is aimed at supporting elderly people with financial difficulties by offering low-cost accommodation and helping them find work, public broadcaster NHK reported.

It is usually unstaffed overnight, according to local media.

As dawn broke, police and firefighters were combing the blackened remains of furniture in freezing temperatures.

“As there were many oil tanks (for kerosene stoves) there, I heard a number of small explosions,” a 67-year-old woman in the neighbourhood told Jiji Press. “Luckily, the only damage to our house was some cracks on the window,” she was quoted as saying.